The present invention relates to an apparatus for collecting and treating carbonated gas in order to deal with so-called global warming or warming-up of the earth, and more particularly to an apparatus for casting collected carbonated gas into an abyss.
It has been considered, as one countermeasure for the global warming, to collect carbonated gas from burnt exhaust gas and to cast it into the abyss, i.e. the sea. For example, in Japanese Patent Laid-Open No. Hei 3-128792, an apparatus and a method are proposed which replace the sea water within a casting tube by gas and thereafter cast carbonated gas into the abyss through the casting tube.
FIG. 14 is an overall schematic view showing an abyssal casting system for carbonated gas. In FIG. 14, reference character 04 denotes a carbonated gas processing plant on the earth, from which liquefied carbonated gas is transferred to a base 05 on the sea by a transport vessel. The liquefied carbonated gas is cast into the abyss through a casting tube 07 from the base 05 on the sea.
However, if the liquefied carbonated gas is cast into the abyss at an extremely low temperature, the sea water is frozen, and there is a fear that not only would an outlet of the casting tube 07 be clogged but also that the sea water around the tube would be frozen so as to be floated together with the liquefied carbonated gas. No countermeasure for this has yet been developed.
In the case where such liquefied carbonated gas is reserved in a reservoir tank under the condition of -55.degree. C. and 0.6 MPa and is cast into the abyss through the casting tube under this condition, if the heat transfer between the periphery of the tube and the sea water is insufficient, the temperature of the liquefied gas would not be raised even at the casting tube outlet and the carbonated gas would be discharged at the low temperature therefore not only would the tip end portion of the casting tube be clogged by the frozen sea water, but also the liquefied carbonated gas would float to the sea surface together with the frozen sea water.
In particular, the upper portion of the casting tube is kept at a lower temperature. The sea water is frozen around the outer surface of the casting tube. Furthermore, the heat transfer from the sea water to the interior of the casting tube is prevented.
Thus, the castable amount of carbonated gas for the constant casting tube is restricted by the amount of the heat transfer with the sea water around the periphery of the tube.
On the other hand, in order to elevate the temperature of the liquefied carbonated gas upon casting, the applied pressure should be increased to maintain the liquefied condition. This condition is a relatively high pressure condition (at 6 MPa, because a saturated pressure at a temperature of 20.degree. C. is 5.85 MPa). However, it is difficult to handle the high pressure gas.
Also, it is necessary to adjust the release pressure to the same pressure as that around the open lower end of the casting tube to prevent the gasification of the carbonated gas in the middle stage. However, it is difficult to carry out the pressure adjustment for preventing the freezing while preventing the gasification.